Air

It's 8am on Sunday morning and i have opened the window to let some fresh air in. As i lay in bed and breathe it in it smells absolutely divine! It doesn't smell 'nice', it doesn't have a strong smell of flowers, clean washing or freshly cut grass, or at least they are not strong enough for my nose to pick them out. So why does it smell so good?
Are the 'nice' smells (mentioned above) blended perfectly so they are subtle enough not to be picked out but give it the overall stamp of 'good' air? Is it because i spent the night recycling the 'old' air in the room, continually adding to the percentage of carbon dioxide, so now the oxygen smells good? Could it be that my body has evolved to reward me for finding oxygen rich air by making it smell, to my percepton, good? This would mean that others would find the smell different, with their brains choosing a smell that they too think is good, but if compared, the smell would be completely different.
Our brains rule our perception of the world, nothing is probably viewed exactly the same by each of us, so which perception is accurate, is true? Maybe nothing is true, it's just what we perceive to be true.
The air coming through that window is divine - fact!